How does rain affect mileage?

[Dngrsone]

Wow... if those numbers are even remotely accurate, I can understand why many people don't meet the EPA estimates.

Thanks, dogfriend.

That would be a fun program to play around with on my T|X...

[JimboK]

Originally Posted by omgitsroy326

can i get a copy???

Not from me. I paid for the application and I'm sure that would be a licensing violation. Besides, he issues a registration code upon purchase that I think is good for only one machine.

[Dngrsone]

Well, hopefully the program will be available again, soon.

[fed123]

Originally Posted by bwilson4web

Rolling drag increases due to pushing aside the road water. There is a loss of momentum from rain that is accelerated to vehicle speed and drops off. The formerly smooth surface is now covered with less smooth water ripples, drops and imperfections. That is just the short list.

Bob Wilson

On the other hand, it might slow down your speed so that you spend more time driving in the mpg "sweet spot."

[donee]

Hi All,

Besides aero drag and rolling resistance, there is also conducted heat losses. In cold weather from the cabin, that the heater has to replace, and also from the radiator. I noticed a few mpg bump in wet weather when I started blocking my top grill openings. I think the top opening acts like a knife edge to guide the water right to the radiator, the hottest part of the radiator, which then gives up the most amount of heat.

[Dngrsone]

I didn't think that I would have to block my grill, seeing as the temps rarely go below 38 F, but even that seems to sap mileage in a noticeable way.

[donee]

Hi Dngrsone,

Heat flows from hot to cold. And the bigger the temperature difference the bigger the heat flow. So, a 180 F radiator will flow allot of heat into a 38 degree raindrop, and the more rain drops, the more heat will flow. Rain is allot more dense than air, and stays in contact with the radiator metal for a longer period, even to the point of evaporation. The heat of evaporation is dramatically more than the heat required to heat the water up to 185 F from 38 F.

It all adds up. I run the top grill block year round below 100 F.

[Rokeby]

In addition to energy losses at the front of the tire --squeegee action, perhaps some infinitesimal rising up a miniscule water hill pushed in front of the tire (At some point the rising would result in hydroplaning), I suspect that sideways horizontal splashing, and lifting/throwing of water behind the tire -- the reason we buy splash guards -- also represent a transfer of energy from the vehicle to rain water on, or formerly on, the road surface.

[Dngrsone]

Originally Posted by donee

Hi Dngrsone,

Heat flows from hot to cold. And the bigger the temperature difference the bigger the heat flow. So, a 180 F radiator will flow allot of heat into a 38 degree raindrop, and the more rain drops, the more heat will flow. Rain is allot more dense than air, and stays in contact with the radiator metal for a longer period, even to the point of evaporation. The heat of evaporation is dramatically more than the heat required to heat the water up to 185 F from 38 F.

It all adds up. I run the top grill block year round below 100 F.

Thanks, donee. Since we here in Central Nowhere hit >100 for a good 30 days or so every year, I might forgo the blocking during the summer.

Now I must source some high-density foam pipe wrap.

[dogfriend]

Originally Posted by Dngrsone

Since we here in Central Nowhere hit >100 for a good 30 days or so every year, I might forgo the blocking during the summer.

Yeah, I've read the info about blocking with pipe wrap and installing a engine block heater, but by the time I get off my a$$, it will be 105°F. I am sure that if I had an EBH, I would try to drive away without unplugging it in the first week.